Friday 14 October 2011 07.29 EDT
First published on Friday 14 October 2011 07.29 EDT

TalkTalk has been reprimanded by regulator Ofcom and threatened with a fine of up to £2m for plaguing customers with silent calls earlier this year.

Silent calls are caused by automated systems known as diallers which are used in call centres to generate and attempt to connect calls.

If there are not enough call centre agents available to handle all of the successfully connected calls, the person on the receiving end of the line is greeted with a silent call.

Ofcom guidelines state that call centres using diallers should play an information message if a call is abandoned to prevent the call being silent, but this does not always happen.

Ofcom said its investigation had given it "reasonable grounds" to believe that in February and March this year TalkTalk persistently made silent calls to its customers.

The regulator has given TalkTalk until the middle of November to respond to the allegations, and to take steps to make sure the problem is not repeated. After this, Ofcom said it will consider fining the company if appropriate. It can levy up to £2m.

TalkTalk said the silent calls were down to a South African company and a sales agency based in Britain it worked with earlier this year. In a statement it said: "TalkTalk no longer works with these sales agencies and, if Ofcom imposes a financial penalty, we will recover this sum from the third party responsible."

In 2010 the regulator received more than 9,000 complaints about silent calls. More than 70% of those who complained told Ofcom they had received two or more calls in a day from the same company. These silent calls were often over a period of days or even weeks.